Drying wood, lumber, and the like



Dec. 29, 1925' J. B. WELCH DRYING woon, LUMBER, AND 'rx-1E LIKE FiledMay 24. 19".4 6 Smau-Sheet l T2 g; W $5 i Si e N l a Il "Il I v .1

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n: ATrORNEYS Dec. 29 1925- 1,567,559

J. B. WELCH DRYIIIG WOOD, LUIBER, AND THE LIKE Filed May 24. 1924 6Sheets-Sheet 2 l f4 6 J/ AMs ATTORNEY:

Dec. 29 1925.

J. B. WELCH DRYING woon, LUuEa, AND 'nm Lrxs Filed Hay 24. 1924 6ShOStB-Shtt 3 DUN BY ZM, M4/MQW@ #lf ATTORNEYS Dec. 29, 1925. 1,567,559

J. a. wELcH DRYING WOOD, LUHBER, AND THE LIKE :med may 24. 1924 ssheets-sheet 4 Movement fedfamsm OPERA TED VA L VE 601. ENO/0 OPERATf V4L VE xNvENToR fda /J MM BY //-f ATTOR NE YS Dec. 29 1925- J. B. WELCHDRYING WOOD, LUKBER, AND THB LIKE Filed lay 24. 1924 6 Sheets-Sheet 51,567,559 J. B. WELCH Filed lay 24. 1924 6 Sheets-.Sheet 6 mvnN-ron@Lef/L Arronnsvs Dec. 29, 1925.

DRYING VIODD, LUIIBER, AND THE LIKE Patented Dec. 29, 1925.

UNITED STATES APATENT OFFICE.N

DBYING WOOD, LUMBER, AND THE LIKE.

Application led Hay IM, 1924. Serial No. 715,516.

To all 'whom it may concern:

Be it known that I, JOHN B. WELCH, a citizen of the United States,residing at New Orleans, in the parish of Orleans, State of Louisiana,have invented certain new and useful Improvements in Drying Wood,

Lumber, and the like; and I do hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use the.same.

This invention relates to the art of drying materials, such as lumber,wood, or the like, and has for its object the provision of an improvedmethod of drying such materials. More particularly, the invention aimsto provide a method of drying materials, such as lumber or Wood, inwhich the temperature and humidity of the drying medium areautomatically controlled in response to changes in a varyingcharacteristic (such as weight or moisture content) of the materialundergoing drying as the drying progresses.

The invention relates especially to the drying of lumber or wood andwill be described throughout this specification as applied to thatindustry. It is to be understood, however, that the principles of theinvention are applicable to the drying of other materials Wheredifferent conditions of temperature and humidity are required in thecourse of the drying operation.

The controlling factors in the drying of lumber, and of wood generally,are the moisture content of the wood, the thickness of the Wood andthe secies. Woods which are easily subject to sp itting in drying must betreated at a low temperature and a high humidity. If the wood hasv ahigh percentage of moisture the starting tem erature must be lower andthe humidity hig er than if the same wood hadbeen air-dried down to alow moisture content before bein put in the drying kiln. Inl otherWords, t e moisture content of the Wood is the controlling factor forany particular thickness and species.

In the careful drying of Wood, the moisture content of the Wood is rstdetermined and the a propriate temperature and humidity of he dryingmedium for that moisture content are thereby established. After the woodhas been dried down to a lower moisture content, more severe conditionsof temperature and humidity of the drying medium are allowable.Heretofore, in the careful drying of wood, it has been necessary for theoperator to periodically go into the kiln, take a sample of the woodundergoing drying, and make a moisture determination of that sample inorder to find out if the moisture content is low enough to permit orwarrant a new setting of, the conditions of temperature and humidity. Inpractice, this necessitates daily weighing of samples from each kiln todetermine the appropriate conditions for the drying o eration. Often,even in the hands of a s illful operator, the drying proceeds too farbefore conditions are changed, and then again conditions are sometimeschanged before the lumber or wood is dry enough to stand the alteredconditions of temperature and humidity.

The high temperatures and humidit within a lum er drying kiln make theuty of entering the kiln for obtaining sam les most arduous, and on thisaccount, the rying is seldom controlled by the moisture content of thewood as it should be, but is more often based on a time schedule. Thisschedule is set after the moisture content of the Wood is determined andbefore drying commences. If everything proceeds without interru tion,good drying may be accomplished. lowever, any interruptions in the dring, such as low steam pressure, shutting own of the kilns or boilersfor repairs, changes in weather conditions which affect the temperaturewithin the kiln, and a variety of other causes, often slow up the actualrying so that the lumber or wood is not able to stand theincreasing'temperature and decreasing humidity called for by the dryingschedule. As a result, there is often a considerable loss of lumber dueto splitting caused by too rapid drying.

The present invention contemplates an improved method of dryingmaterials such as wood or lumber in which the material itself, accordingto its moisture content, from within the drying kiln, automaticallyprescribes the appropriate temperature and humidity conditions which arerequired throughout the entire drying operation. Thus, the inventioninvolves the control and ad'ustment of the conditions of temperature anhumidity of the drying medium in response to the decreasing moisturecontent o the material undergoing drying. In carrying out the invention,an appropriate representative sample of the material undergoing dr ing,such as a slab where lumber is bein ried, is subjected to the action ofthe drying medium in exactly the same manner as the entire bulk ofmaterial being dried and is operatively associated with appropriatecontrol instrumentalities without the kiln for effecting redeterminedchanges in the conditions ofp temperature and humidity within the kilnas the moisture content of the sample decreases.

The novel features of the invention will be understood from thefollowing description taken in conjunction with the accompanyingdrawings which illustrate what I now deem to be the best modes ofcarrying out the invention. Iri the drawings:

Fig. 1 is a diagrammatic perspective View of a lumber drying kilnequipped for the practice of the invention,

Fi 2 is a diagrammatic View of the control mstrumentalities of Fig. 1,

F ig. 3 is an enlarged view of the main controlling switch, and

Figs. 4, 5 and 6 are diagrammatic views of modified arrangements ofcontrol instrumentalities.

Referring to Fig. 1 of the drawings, the kiln proper comprises anenclosed brick structure 5. The side walls of the kiln are provided withflues 6 open to the atmoshere at their upper ends and communicat- 1ng byports 7 with the interior of the kiln. The ports 7 are controlled bymovable dampers 8 attached to an operating rod 9 extending through oneend of the kilns.

A series of steam vpipes 10 are placed on the fioor of the kiln and areappropriately connected to a steam main 11 outside the kiln. The steampipe 11 is rovided with a control valve 14. A series o spray pipes 12are also arranged within the kiln and communicate with a supply main 13outside the kiln. A control valve 15 is placed in the spray pipe 13.

The lumber 16 to be dried is piled on a truck 17 arranged to run uponand be supported by rails 18 Within the kiln'. Preparatory to the dryingoperation, the lumber is appropriately piled on the trucks and these arethen run into the kiln. The control sample is then arranged to actuatethe control instrumentalities in accordance with the principles of thepresent invention and the kiln is then closed and in ordinary operationneed not again be opened until the lumber is completely dried.

The control sample 19 is a representative sample of the wood to be driedand'may conveniently be ap roximately eight inches wide and twentyourinches long. This sample is placed on a special t pe of scales withinthe kiln. The sample 1s preferably so positioned that the action thereonof the drying medium within the kiln is fairly representative of-theaction of that medium throughout the kiln.

The sample 19 is carried by a pair of depending grab hooks 20 pivotallymounted near one end of a horizontally positioned balance arm 21. Thebalance arm is operatively supported by a pair of stationary knife edges22 cooperating with notches near the other end of the arm and by astationary knife edge 23 above the arm and intermediate its ends butrelatively nearer the end cooperating with the knife edges 22. The edgeof the ivot 23 cooperates with a V-shaped recess 1n a cylindrical block24. The block 24 is surrounded by and secured to a tube 25. A iiexiblestrap 26 is secured at one end to the tube 25 and passing over the topof the tube is fastened at its other or de ending end to the balance arm21.

A ependig rod 27 is secured to the tube 25. The rod 27 is screw-threadedat its lower end and a counterweight 28 is threaded thereon. The tube 25(or rod 27, as desired) carries a pointer 29 arranged to sweep across acooperating stationary scale 30.

The stationary knife-edge pivots 22 and 23 and the scale 30 mayconveniently be mounted on a portable anel 31. This panel may alsoadvantageous? carry the electrical controlling switch or ot er device ofthe instrumentalities for transmitting movements of the balance arm 21to a desired ointvoutside the kiln. Fig. 3 of the drawings is an enlared view of the controlling switch illustratedl in Figs. 1 and 2. Thisswitch comprises a movable metallic rod 32 connected at one end by meansof a pivoted link 33 to the rod 27. The rod 32 carries a relatively longcentral contact member 34 and two short contact members 35 and 36. Thecontact members 34, 35 and 36 cooperate with predetermined pairs ofcontact members mounted on the inner surface of a rotatable hollowcylinder 37 of insulating material, such for example, as bakelite. Thehollow cylinder 37 shown in Fig. 3 has two )airs of contact members, butit is to be un erstood that the hollow cylinder may, if desired, beprovided with only one pair of such contact members, but usually will beprovided with a plurality of airs of such contact members. As shown inig. 3, there are ten contact members (fz-1- and b-1-2-3-4-5) in one pairand s1x (c-1-2-3 and d-1-2-3) in the other.

The contact members of the cylinder 37 extend through the wall of thecylinder and :,semso are adapted at the -outer surface 'of the cylinderto engage with ap ropriate contact brushes carried at the en s ofconductors (e-1-2-3-4-5-6-7-8-.9-10 These conductors are mounted in blocs 38 and are connected to insulated wires designated in the drawings bythe same reference numerals as the corresponding conductors. y

The cylinder 37 is mounted to turn or rotate in a cylindrical support orbearmg provided by the members 39 and 40. The entire controlling switchis enclosed in a cylindrical casing 41, closed at one end by a cap 42,which also provides a bearing for the movable rod 32. The other end ofthe casing 41 is closed b a cap 43wh1ch rovides a bearing for t 1eextended end o the cylinder 37, to which end is secured a knob 44 forturning the cylinder.

The cylinder 37 carries near its center a circumferential contact ring45 which is electrically connected to the contact member 34 and engagesa stationary contact 46 carried by the member 39. A conducting wire 17is connected to the contact 46.

The conductors e-1-2-34-5 are connected to one terminal of the fivecoils of a solenoid 48. The other terminal of the five coils of thesolenoid 48 are connected by a common conductor 49 to one terminal of abattery 50 or other appropriate source of electric energy. The othertermnial of the battery 1s connected to the conductor 47. Similarly, theconductors e-67-89-10 are electrically connected to the five coils of asolenoid 51.

The movable armature 52 is adapted to move a counterweight 53 along thearm 54 of a regulator 55. The regulator 55 is operatively connected tothe control valve 14. As shown in Fig. 2 of the drawings, the valveregulator 55 is of the diaphragm type. The expansion-contraction chamber56 of the regulator is operatively connected with a temperatureresponsive device 57 positioned within the kiln. The device 57 may beany of the well-known types of expansion and contraction thermometers.As represented in the drawings, the device 57 is of the gas type andexpansion and contraction of the gas in the device, in response tochanges 1n temperature to which the device is subjected, is transmitteddirectly to the chamber 56 of the regulator. The regulator also includesthe pivoted balance arm 54. This armis secured to the valve actuatingstem of the regulator, and the position of the weight 53 on the armdetermines or sets the counterbalancing action and therefore the adjustkment of the control valve 14.

The movable armature 58 of the solenoid 48 is adapted to move a weight59 along the balance arm 60 of a regulator 61. The expansion-contractionchamber 62 of this regulator is operatively connected with a'wet bulb ortemperature responsive device 63.

The device 63 includes a wick 64 dipping into a receptacle 65 containingwater. By meansyof the wick 64 the surface of the device 63 is alwa scovered with a film of water. In the umher dr ing industry, it iscustomary to call the rlisvice 63 the .wet bulb `and the device 57 thedry bulb.` The wet bulb 63 is positioned within the kiln as indicated inFig. 1 of the drawings.

The outer end of the balance arm 60 is connected by a link 66 to amovable contact 67. The contact 67 is arran ed to connect the terminalof one of the ve coils of a solenoid'S to a battery 69, or other sourceof electric energy and to the common terminal 70 of the solenoid coils.The movable armature 71 of the solenoid 68 is arranged to actuate thevalve 15 for the spray pipes 12 within the kiln. The armature 71 is alsoarranged to actuate the rod 9 of the dempers 8. These various elementsare more or less diagrammatically indicated in Figs. 1 and 2 of thedrawings for the sake of simplicity.

In its two extreme positions (upper and lower as shown in Fig. 2) thecontact 67 isarranged to energize the right-hand coil of the solenoid68. W'hen this coil is energized the position of the armature 71 is suchthat the ports 7 are completely closed by the dampers 8 and the valve 15is open full. In its uppermost position the Contact 67 also effects theringing of an alarm bell 72. Moving from its right-hand towards itslefthand position, the armature 71 of the solenoid 68 gradually closesthe valve 15 and consecutively adjusts the damper 8 so that the port 7is one-fourth open, one-half open, three-fourths open and full open.

A control sample 19, which is representa tive of the Wood to be dried,having been selected and its moisture content determined, is placedbetween the grab hooks 20. The position of the Weight 28 is thenadjusted upon the rod 27 so as to balance the control sample 19 andplace contact members 35 and 36 in operative association with contactmembers a1 and 51 respectively, which through their electricalconnections actuate means for establishing the initial conditions oftemperature and humidity for the drying operation. If one inchA gum,having a moisture content of 200% based on bone dry weight, is to bedried the initial temperature of the kiln, or

dry bulb temperature. should be 160 F,

and the humidity should be such as correspends to al wet bulbtemperature of 155 F. Y With contact members 36 and b1 engaging eachother, the circuit through the coil at the left of solenoid 51 willbec'losed, thereby attractin the movable armature 52 moving the Weig t53 to an appropriate predetermined position upon the arm 54 tocounterbalance the gas pressure within the chamber 56. This position ofthe weight 53 has been i l gas in predetermined to` maintain a dry bulbteiliperature of 166 F.- If the temperature within the kiln rises, theincreased pressure within the dr bulb 57 is transmitted to the vulveregu ator to close the valve 14.

As the control sample 19 dries a predetermined amount, contact member 36moves to the left to engage contact member b and closes the circuitthrough the next adjacent coil of solenoid 51. The counterbalance weight53 is thereby moved further out on the arm 54 a predetermined amount t-ocounterbalance a greater gas ressure within the dry bulb 57 and the vave regulator 5,5 to correspond with `an increased temperature within thekiln, for exam le, 170 F. AS the wood being dried (or t ie controlsample 19) continues to dry further down to its final moisture content,the contact member 36 moves to and consecutively engages contact membersb, b, etc., thereby establishing the appropriate drying temperature asrequired by t e moisture content of the Wood. The arm 54 has )reviouslybeen calibrated so that each of the various ositions of the weight 53thereon establis es and maintains definite temperature conditions withinthe kiln.

For each position of contact. member 36 there is a correspondingposition for contact member 35. Thus, while contact member 36 engagescontact member b1, contact member 35 will engage contact member a1 toestablish the appropriate initial humidity conditions for drying. Theoperation for the control of humidity is in principle the same as forthe control of the temperature. Thus, as contact member 35 engagesconsecutively contact members al, o2, etc., the circuits through thecoils from the right to the left of the solenpid 48 respectively will beclosed to attract the armature 58 and move the Weight 59 to appropriatepositions on the arm 60 to counterbalance the expansion and contractionof the regulator 61 operated by the expansion and contraction of the theWet bulb 63, which is placed in the position where the humidity is to-be controlled. For a constantly decreasing humidity the wet bulb temrature is lowered as the drying procee s, therefore the weight 59 is seton the arm 60 progressively nearer the regulator 61.

If for any reason the humidity within the kiln varies from the desiredpoint, for example increases, the wet bulb temperature increases causingthe gas pressure to increase, raising the outer end of the arm 60. Thelink 66 and movable contact 67 rises accordingly to close a circuitthrough one of the coils of the solenoid 68, which attracts the armature71 and moves the rod 9 to partially shut the valve 15 to the spray andopen the dempers 8. If the humidity still rises, the wet bulbtemperature Will amamos continue to rise and the expansive force in thewet bulb will raise the movable contact 67 to close the circuits throughthe coils of 4the solenoid 68 to move the rod 9 until the d am ers 8 arewide open and the spray is tight y shut. The apparatus will remain inthis condition until the humidity Idrops to the desired point, and if itfalls below the desired point, the temperature at the wet bulb willdecrease to such an extent that the contraction of the gases in the wetbulb will reduce the pressure within the regula.- tor 61 sufficiently toallow the movable contact 67 to lower again to close the circuitsthrough the various coils of the solenoid 68 and operate the dampers andspray as needed.

Ify by chance the water supply to the wet bulb fails, the wick on thewet bulb becomes dry and this bulb then o rates as a dry bulb. This isan excee 1n ly dangerous condition for the wet bul temperature would beequal to the dry bulb. Under such circumstances, that is, whenever theWet bulb controller goes higher than the desired setting, normally thedempers would be Wide open and the sprays off. To provide against thisthe movable contact 67 will close a circuit through an alarm bell 7 2and the coil at the right of the solenoid 68 to close all dempers andopen all sprays, and thereby When this occurs, the alarm bell noties theoperator that the wet bulb has gone dry, but assures that his lumber isprotected by means of the open spray and closed dempers. Instead ofruining the wood by rapid drying, the drying is merely slowed down untilthe operator can restore the flow of water to the wet bulb.

It will be understood that for each movement of the armature 58 withinthe solenoid 48 with simultaneous setting of the counter balance Weight59, the movable contact 67 will assume a position corresponding theretoso that the solenoid 68 will move the armature 71 to a position withinthe solenoid 68 corresponding to the position of the armature 58 withinthe solenoid 48.

In the modified arrangement of control in'strumentalities illustrated inFig. 4, I have provided means whereby the instrumentali-Y ties,including the rod '32 and the Contact members 34, 35 and 36 which aremoved in response to a change in a characteristic of the material beingdried, may be placed outside of the kiln walls 5. This is accomplisliedlby the provision of a synchronous movement mechanism of theelectrodynamic type or of a mechanical type. In Fig. 4 of the drawingsthe synchronous movement mechanism is of the electrodynamic type andcomprises two electrically connected induction devices 73 and 74 soarranged that movement of the rod 7 5, which is connected protect thedrying of Ithe wood.

to rod 27, is synchronously transmitted `to the rod 32.

Fig. 4 illustrates a `further modification in the controlinstrumentalities previously described whereby an electrically operatedtemperature controller 76 and an electrically operated humiditycontroller 77 may be employed. f

'Iyhe conductors e1, e2, es, e, and e are connected to one terminal ofthe five coils of an electromagnet 78 associated with the` electricallyoperated temperature controller 76. The other terminal of the five coilsof the electromagnet 78 is connected by a comino-n conductor 49 to oneterminal of a battery 5() or other source of direct current. The otherterminal of the batter is connected to the conductor 47. Similarly, theconductor e-6-7-8-9-10 are electrically connected to the five coils ofan electromagnet 79 associated with the electrically operated humiditcontroller 77.'

The ry bulb 57 is operatively connected to the open end of a helix 80which is secured to the shaft of the indicating pointer 81 of thetemperature controller 76 so that a variation in the gas pressure fromthe dry bulb turns the pointer 81 to indicate the temperature Within thekiln The temperature controller 76 carries an arm 82 pivoted at one endand having a contact 83 adapted for association with the coils of theelectromagnet 78. The arm 82 and pointerxSl carry contacts 84 adaptedfor engagement when the pointer 81 moves opposite the arm 82. Thecontacts 84 lare electrically connected through a battery 85 to a relay.The relay is operatively connected to an electrically operated valve 86,either motor-driven or-actuated by a solenoid, in pipe 11 forcontrolling the steam supply to pipe 10 within the kiln. A small by-passpipe 87 having a hand operated valve 88 is provided in the` pipe 11circumscribing the Valve 86 to permit a small amount of steam to gothrough the pipe 11 when the valve 86 is closed.

The wet bulb 63 is operatively connected to the open end of a helix 89of the humidity controller 77. The construction of the humiditycontroller is identical with the temperature controller 76 and comprisesa pointer 90, and an arm 91 having a contact 92 adapted for associationwith the coils of the electromlagnet 79.

The humidity controller 77 is provided with. an additional pointer 93associated with the helix 89. An additional arm 94 is also providedcarrying a contact 95 adapted for association with the coils of anelectro magnet 96 which are electrically connected to conductors641-2-345.

Pointer 90 and arm 91 are provided with contacts 97 which engage whenthe pointer 90 moves opposite arm 91. Likewise, pointer 93 and arm 94are provided with contacts The force of steam in the valve 102 causesits diaphragm to ex and and actuate a lever arm 103 to close amper 104against its counterbalance 105.` n

The operation of the apparatus illustrated in Fig. 4`is the same inprinciple as that illustrated in Figs. 1, 2, and V3. At the start of thedrying operation, contact member 36 en ages contact member b1 to closethe circuit through the right hand coil of electromagnets 78 and 96which attract contact 83 on arm 82 and contact 95 on arm 94respectively. This sets arms 82 and 94 'at t e same temperature positionwhich is the dry bulb temperature The steam valve 86 is open so thetemperature in the kiln contiues to rise untll the pointer 81 movesopposite arm 82 and contacts 84 engage to close the circuit through therelay. The relay then energizes the solenoid of valve 86 to shut oil'the steam supply to pipes 10 until the temperature within the kiln fallsbelow the point at which cont-acts 84 engage, The circuit through therelay will now be opened and the solenoid operated valve 86 will also beopened so as to allow steam to pass into pipes 10.

When contact member 36 engages contact member b1 contact member 35engages contact member a1 to close the circuit through the right handcoil of solenoid 79 which attracts contact 92 on arm 91. If the humiditybecomes lower than the point set by arm 91, the temperature of the wetbulb 63 rises and 97 engage to c ose the circuit through the relay andenergize the solenoid of valve 100 and allow the spray to enter thekiln, and at the same time allow steam to pass to the motor dam er valve102, causing the damper 104 to c ose.

If the sup ly of water to the wet bulb should fail, t e wet bulb wouldgo dry and the revisions for the control of humidity wou d not operateas contemplated. Under such circumstances the wet bulb would operatelike the dry bulb and the gas ressure therein would increase to causepointer 93 to approach arm 94 until contacts 98 engage. The circuitthrough the relay would now be closed, and the valve 100 opened, exactlyas in the case of low humidity, and the alarm bell sounded.

bers 34, 35, and 36 on the rod 32 are always started from the samepositions within the cylinder 37 regardless of the moisture content,thickness, or species of wood, or other material being dried. It issometimes desirable or necessaryto starter stop the drying operationunder different conditions of temperature and humidity. For example,when drying one inch gum having an initial moisture content of V200 percent, based on bone dry weight, the initial dry bulb temerature shouldbe about 160 F. and the wet mlb temperature about 155 F. Then dryingwood or other material having a dill'erent initial moisture content,thickness, or different species, the conditions of temperature andhumidity, or dry bulb and wet bulb temperatures, at the start and finishof the drying operation must be different if satisfactory drying is tobe accomplished. These conditions may be brought about by eniployingdiierent pairs of contact members engaging contact members 35 and 36.lVhen employing contact members af-1-2-3-4-,5 and 7)-1'-2345 engaged bycontact members 35 and 36 respectively, an initial dr bulb temperatureof 160o and wet bu b temperature of 155 F. is secured and a finishingdry bulb temperature oi 180 F. and wet bulb temperature of 150 F. When alower initial and a higher finishing dry bulb and wet bulb temperaturesare necessary or desirable, I replace contact members a1-234-5 andb-1-,2-3-4-5 by a different pair of contact members, such for example,as contact members c-1-2-3 and d-1-2-3. This may be clone by turningknob 44, as shown in Fig. 3, until the appropriate pair of contactmembers are in. the position there occupied by the contact members(1/-1-2-3-4-5 and b-1-2-3-4-5. It will be clear that when the contactmembers c-1-2-3 and d-l-a-S are thus turned to operating position,contact members c1 and d1 willy close the circuit between contactmembers 35 and 36 and the conductors previously engaged by contactmembers n? and b2 respectively when the latter were in operatingposition. Likewise, it will be observed that any initial or finishingdry bulb and wet bulb temperature may be obtained by merely turning theknob 44 until the appropriate pair of contact members are brought to oerating position within the cylinder 37, t ere being a pair of contactmembers suitable for each initial moisture content, species, orthickness of material to be dried.

The movement of the scale arm 27 is relatively slow, and the electricalcontacts controlled by the scale arm are consequently retained 1nengagement for some length of time. As a result of this condition, thewindings of the various Asolenoids in the control instrumentalities areenergized for a corresponding length of time, and I have Loir/.see

found that this ma lead to difficulties as a result of undue eating ofthe solenoid windings. In Fig. 5 of the accompanyingr drawings,l thereis represented a control equipment in which the slow movement of thescale arm produces ra id energization of the solenoid windings fol owedimmediately by inter-ru tion of the circuit connections o the win ings,although the scale arm contacts may be engaged for sometime thereafter.In other words, there is a quick make-and-break of the solenoid windingcircuits for a slow make-anrl-break of the scale arm contacts.

The scale switch, as diagrammatically represented in Fig. 5 comprises aseries of contacts 110 electricall connected to one terminal of asolenoi( or relay winding 112, and a second series of contacts 111electrically connected to one terminal of a solenoid or relay winding113. The other terminals of the windings 112 and 113 are electricallyconnected to a movable contact 114 actuated by the scale arm 27. Abattery 115 is in the common circuit connection between the contact 114and the windings 112 and 113.

An armature piston 116 is operatively arranged to be moved towards theleft (Fig. 5) when relay winding 112 is ener ized and towards the right(Fig. 5) when re ay winding 113 is energized. The piston 116 carries apin 117 engaging i'n a slot in a rocker cam 118 so that when the winding112 is energized the cam is turned counter-clockwise, and when thewinding 113 is energized the cam is turned clockwise. A spring -119mechanically connects the cam 118 with a movable switch arm 120 adaptedto engage with either of two spring contacts 121 and 122. The cam 118 iselectrically connected to the movable switch arm 120 through themetallic frame of the instrument or through the spring 119.

The cam 118 carries two lugs 123 and 124 adapted to engage with and lockthe switch contacts 121 an 122, respectively, in such a manner that theiston 116 can move almost its com lete distanceI towards the windin 112or the winding 113) before the spring 119 will act to throw the arm 120from engagement with contact 121 into engagement with contact 122, orvice versa.

The piston 116 carries a flexible Contact 125 arranged to have asweeping engagement with a stationary contact 126, as the piston ismoved in response to the energizetion of first one and then the other ofthe windings 112 and 113. The contacts 125 and 126 are included in anelectrical circuit with a battery 127 and a solenoid or relay winding128.

An armature plunger 129 is operatively mounted with respect to thewinding 128. At its lower or outer end the Aarmature 129 is pivotallyconnected to a lever arm 130 which in turn is pivotally mounted on ashaft or spindle 131. The lever arm 130 carries a Spring-pressed pawl132 cooperating with a ratchet 133 secured to the shaft or spindle 131.A holding p awl 134 is also mounted in operative engagement with theratchet 133. Setting screws 165 are provided fordetermining the movementof thel armature 129 each time the winding 128 is energized. Adjustmentof the permits adjustment of the number of! teeth of the ratchet 133moved each time the windin 128 is energized.

he ratchet 133 is always moved in the same directionbytlie armature 129.A cani 135 is secured to the spindle 131. Movement of the cam 135actuates a cam lever arm 1.36l A pointer-5 82 is also secured to theshaftf 137. 1 A- secured to a shaft or spindle 137.

spring 13S (secured at one end to thepointer 82') is arranged to holdthe cam follower of the lever 136 against the cam 135.

A block of insulating material 139 is also secured to the shaft 137 andis accordingly moved with the pointer 82. Electrical contact arms 140and 141 are secured to and carried by the block 1.39. An indicatingpointer 81 is operatively associated with the dry bulb (or wet bulb)Within the kiln `and is actuated in response to changes in temperatureor humidity) Within the kiln. The pointer 81 carries an electricalcontaeter 142 adapted to engage with either of the arms 140 and 141.

When the solenoid winding 128 is energized (in response to predeterminedmovements of the scale arm 27), the ratchet 133 is turned apredetermined amount, which is equal for each movement of the plunger129. This turningof the ratchet sets the contact arms 140 and 141 to apredetermined temperature indicated on the scale 143 by the pointer 82.It willy be observed that byusing the cam arrangement a variablemovement of the pointer 82 is obtained for equal movements of theratchet, and this is necessary because the scale for the temperaturecontroller is not uniform. When the temperature element or dry bulb inthe kiln operates the pointer 81', the contacter 142 engages with thecontact arm 140 or 141 and this opens or closes the valve on the steammain. For this purpose, it Will be understood that the contacts 140, 141and 142 are included in appropriate electrical circuits for actuatingthe valve on the steam main. The pointer 81 and temperature element andcooperating equipment may be of any usual temperature indicator orcontroller type. The contact arms 140 and 141 are provided with springs144 for pulling these arms back when the pointer 81 returns to itsneutralposition.

By making contacts 110 and 111 operate the ratchet 133 and cam135 forcertain perboth humidity and temperature. as well as l take care of Inthis way, about operation of the cam 135, regardless of the thickness orthe kind of wood, foi` moisture contents of 100%, 20%, 40%, 30%, 25%,20%, 15%6 10%. The cam 135l can thus be designed to give any desiredschedule of tem erature and humidity control.

It will e understood that the pointers 81. and 82 correspond in functionwith the pointers 81 and 82 of Fig. 4 of the accompanyin drawings.Itwill also be understood t iat the` same type of control equipment maybe used in conjunction with the yvet bulb instrument as with the drybulb instrument.

In Fi 5 of the accompanying drawings, I have s own a construction ofscale switch which I prefer to employ in conjunction with the equipmentillustrated in this Figure 5. Corresponding parts in Figs. 2 and` 5 areindicated by the same referencey numerals. The contacts 11() are carriedin the top segment of a ring of insulating material 145, preferably madeof bakelite. The contacts 111 are carried in the bottom segment of therin 145. The .movable contact 114 (connected to the pivoted link 33) isarranged to alternately engage with the contacts 110 and 111. It will beunderstood that the contacts 110 and 111 are positioned in .the ring atthe percentage points Where it is desired to change the temperature andhumidity conditions as hereinbefore described.

As the moisture driesfrom the sample 19, the arm 27 moves toward avertical position and this movement is so transmitted to the contact 114that the contacts 110 and 111 are alternately engaged. This results inthe periodic energizatiou of the winding 128 with the attendant resultshereiiibefoie described.

In Fig. 6 of the accompanying drawings there is diagrammaticallyillustrated a comthe variable scale gradustions.

pressed-air equipment for carrying out my present invention. c Thisequipment comrises an automatic regulator 146, operated y compressedair, and controlled by the weight of the sample of material (19) beingdried, the initial moisture content of which is known, but the size ofthe sample being capable of variation within reasonable limits. Theautomatic regulator functions in such a way as to maintain at all timesin an air line 147 a pressure that;V corresponds uantitatively to t eper cent of moisture in t e sample 19. This variable air pressure in theline 147 is then used to set the valves controlling the temperature andhumidity within the kiln.

the contacts 110 and 111 bring The regulator 146 is o erated' by a scalebeam 21', balanced on a-mie edge 148 fitting in a bearing fixed `on asupporting frame 149, this knife edge being near one end of the beam.The beam is counterweighted to bala'nee with all attachments iu place,The sample 1i) is hung or supported by a suitable holder swinging from aknife edge support 150 on the long end of the beam. 'lhe support 150 ismovable along the length oli' the beam as a result of engagement with athreaded rod` 151 mounted in suitablebearingson and parallel to thebeam. (ln the opposite side of the main ulcrum the rod 151 is threadedin the opposite direction and a munten weight 152 is moved along thisendof the beam as a result of its threaded engagement with the rod. Theratio of the pitches ot' the two threads on the opposite ends of the rod151 are in inverse proportion to the ratio of the weight of the movingsupport 150 and suspended holder to that of the moving counter-weight152, since this will keep the beam always in balance no matter what theposition of the holder when unloaded. Hence, the sample is at all timesthe only thing throwing the beam out of balance. The rod 151 can beturned by means of a knurled nut 166 secured thereto.

The main beam has stops so that its maximum travel at the point furthestfrom the fulcrum is perhaps one-half inch to onefourth inch.

The weight of the sample is supported by a small short flexible rod 153,the upper end of which has a knife edge engagement with the long end ofthe beam 21 near the fulcrum. A round flat disk 154 and c0- operatingrubber or metal diaphragm 155 close. the top of the air chamber of theregulator 146 and are operatively attached to the rod 153. 'l`he lowerend of the rod 153 terminates in an adjust able cone fitting into andadapted to close a corresponding opening in the bottom of the regulatorair chamber, thus constituting a needle release valve 15G, but seat andplug taper inwardly and not outwardly as is usual. The projected area ofthe top of this cone is small compared with that of the disk. y

Compressed air is supplied to the air chamber of the regulator 146 fromany suitable source. In Big. 6, I have illustrated a compressed-airstorage tank 157 adapted to deliver compressed air to the line 147. 'lhecompressed air is supplied to the regulator in such volume that at thelowest pressure in the air chamber all of the air supplied can escapethrough the needle valve 156 if open all the time. Since air is enteringthe regulator all the time, the pressure in the air chamber will riseuntil the pressure on the bottom of the disk in ex-` cess of that on theneedle valve overcomes the weight of the sam le, and the beam will lift.But this will open the needle valve and lower the pressure. However, nowthe beam will immediately fall and close the valve and thus maintain thepressure. Actually, the needle valve will open just enough to allow theair to escape at such a rate as to kee the pressure just. suttieient tol'balance t e weight of -the sample, thus maintaining the beam always inbalance.

One might balance the beam by means of a needle valve Haring outward inplace of the disk and rubber diaphragm, but such an arrangement is notparticularly sensitive because the effective. area varies with theamount of opening. It is well-known that a safety-valve, once o en, willnot seat -until the pressure has fal en quite a little below that neededto open it.

For any articular point of suspension of the samp e on the beam, the airpressure necessary to balance the beam is proportional to the weight ofthe sample. If for a specific sample containing 50% moisture, wet basis,the corresponding air pressure is say 20 pounds, then when this sam leis bone dry, it will weigh half as muci and the air pressure will be say10 ounds. The air pressure gauge 167 is prefera ly calibrated to readdirectly in percent moisture, with the zero reading at say 1() oundspressure. If now a new sample of ifterent size, but still containing 50%moisture, wet basis, be put on the scale beam, one can adjust thepressure to the proper point, corresponding to say 20 pounds airpressure, by moving the knife edge on which thesample swings in or outon the beam, as the ease requires. lVhen the sample is dry, the ressurewill have fallen to 10 pounds, am intermediate moisture contents will beaccompanied by corresponding proportionate differences in air pressure.

In operating this control equipment, the sample is first mounted on thescale beam and the air turned on to the regulator. The sample is movedin or out along the beam by means of the adjusting rod 151 until thepressure gauge 167 shows the moisture content which the sample is knownto contain as determined by previous test, making certain that the airis escaping properly from the needle valve. From now on the position ofthe indicating pointer of the (pressure gauge will at all timescorrespon to and indicate the moisture content of the sample at anyparticular time in question. Hence in each particular case, only oneadjustment is necessary, for variation, both in size of sample and ininitial moisture content.

The air from the needle valve should prefbut should preferably erablynot escape directliyi/ to the atmosphere,

rst escape into an auxiliary chamber from which it makes its final escae through an orice of such size that it wi l build up in this auxilliarychamber a pressure much less than that corresponding to bonedry weightof the sample, yet always in excess of some definite ligure, say onepound. This auxilliary chamber should preferably be connected with asecond pressure gauge, which, should the pressure fall below `thecritical point, will set oil an alarm and shut oil' the heat su ply of-the wkiln. This eliminates danger o failure to function through failureof the air supply.`

If desired, the needle valve of the air regulator may be operated fromthe lower part of the scale beam, but it then becomes less easy to usethe air escaping from it to operate a safety mechanism. It will, ofcourse, be understood that the air regulator mechanism may be widelyvaried in construction.

The air control ui ment posssesses the advantage of very s igit movementof the sample coupled with large changes in operating air pressure.Except for short connections to plug-in points, the air pipes may bepermanently located in the kiln. The relatively long scale beam makes itpossible to locate the sample in the middle of the pile, and still havethe main mechanism in the passage-wa Regulation o the air pressure inthe line 147, in response to variations in the moisture content of thesam le 19 undergoing drying, simultaneously e ects the same regulationof the air pressure in the air line 159 which is connected to the airpressure elements of the dry bulb instrument 160 and the wet bulbinstrument 161. The instruments 160 and 161 may be identical inprinciple oi operation and construction, except that the wet bulbinstrument operates at a lower teinperature, due to the evaporation fromthe wick, than does the dry bulb instrument.

The instruments 160 and 161 may be generally of the usual type of temerature controller. The only additional e ement to the usual temperaturecontroller is a pressure element 162 and a cam 163. The ressure element162 registers the pressure o the air in the air chamber of the regulator146 and hence the moisture content of the sample undergoing drying. Thecam is operated by the pressure element 162 and is designed for anydesired temperature schedule. When the cam 163 is moved by the pressureelement, it operates to set the control pointer 164 of the temperaturecontroller.

The pressure element and cam may be incorporated in any suitable t e oftemperature controller, either electrical or air operated. 'lheseadditional instrumentalities may be easily arranged to set the convThusthe instrument 160 functions to maintain the redetermined temperatureconditionsV wit in the kiln in accordance with the automatic settin ofthe control pointer 164, and similarly t e instrument 161 functions tomaintain the redetermined conditions of humidity wit in the kiln.

The regulator 146 is rovided with a pressure gauge 167yprefera lycalibrated to read in percent moisture. The controllers 160 and 161 arealso provided with pressure gauges 168 agprolpriately calibrated. Theequipment is rt er provided with safety valves, drip wells, air filters,reducing valves and the like as required and as will be understood bythose'skilled in the art. The control valves for the steam heatinsystern, spray system and damper may e of any appropriate constructiondesigned to be actuated by the controllers 160 and 161.

From the foregoing description itwill be seen that, in accordance withthe present invention, the lumber or wood itself, or other materialbeing treated, automatically prescribes the proper conditions oftemperature and humidity within the kiln as the drying operationprogresses. The invention eliminates the need of anyone entering thekiln after the drying operation begins for the purpose of securingsamples to determine the progress of the drying o eration. Moreover,regardless of whether t e operating conditions have been such as to slowup the drying, the control sample will not prescribe a highertemperature or lower humidity within the kiln until the moisture contentof the material being dried is lowered to the point where new and moresevere conditions ofbltemperatnre and humidity are permissi e.

lVhile I have herein particularly described the invention as a plied tothe automatic control of the con itions of both temperature and humiditywithin the kiln, it is to be understood that the invention is equallyapplicable to the automatic control of either one of these conditions inresponse to characteristic changes in a representative sample of thematerial being dried, in accordance with the hereinbefore describedprinciples of the invention.

It will be understood by those skilled in the art that the principle -ofthe invention is capable of being practised with various types andconstructions of control instrumentalities. In this specification, Ihave described those control nstrumentalities which I pow the preferredmodes of Vtrols on the automatic temperature and hulll carryi ouf theinvention. It will be understoo that the invention is not to be limitedto the articular control instrumentalities herein escribed. If desired,the control sample (19) may be suspended by a wire through anappropriate opening in the `roof of the kiln so that all of the controlinstrumentalities may be located outside the kiln.

I claim:

1. The improvement in the kiln drying of materials which require varyingconditions of temperature and humidity in the course of the dryingoperation, which comprises producing an action indicative of changes insaid material as the drying operation progresses, and employing saidaction to establish the desired varying conditions of temperature andhumidity within the kiln as the drying operation progresses.

2. The improvement in the kiln drying of materials which requiredifferent conditions of temperature and humidity as the drying operationprogresses, which comprises producing an action responsive to theprogressive loss in moisture of said material as the drying operationprogresses, and employing said action to progressively establishpredetermined different conditions of tempera-l ture and humidity Withinthe kiln as the drying operation progresses.

3. The improvement in the kiln drying of materials Which requiredi'erent conditions of temperature and humidity as the drying operationprogresses, which comprises producing Within the kiln a continuingaction responsive to the progressive loss in moisture of arepresentative sample of said material as the drying operationprogresses, and employing said action to progressively establishpredetermined different conditions of temperature and humidity withinthe kiln as the drying operation progresses.

4. The improvement in the kiln drying of materials which requiredifferent conditions of temperature and humidity as the drying operationprogresses, which comprises producing within the kiln a continuingaction responsive to the progressive loss in moisture of arepresentative sample of the material being dried as the dryingoperation progresses, and causing said action to establish and maintainpredetermined different conditions of temperature and humidity withinthe kiln :is the drying operation progresses.

5. The improvement in the kiln dryingr of materials Which requirevarying conditions ottemperature and humidity in the course of thedrying operation, which comprises predeterming the desired varyingconditions of temperature and humidity for the material to be dried,producing an action indicative of changes in a varying characteristc ofthe material being dried as the drying operation progresses, andemploying said action to establish the desired predetermined varyingconditions of temperature and humidity Within the kiln as the dryingoperation progresses.

6. The improvement in the kiln drying of materials which require varyingconditions of temperature and humidity as' the drying operationprogresses, which comprises producing an action indicative of changes ina varying characteristic of said material as the drying operationprogresses, and causing said action to establish and maintain thedesired varying conditions oi temperature and humidity within the kilnas the drying operation progresses.

7 The improvement in the kiln drying of materials which require diierentconditions of temperature and humidity as the drying operationprogresses, which comprises predetermining the desired differentconditions of temperature. ad humidity for the material to be dried,producing an action indicative of changes in a varying characteristic ofthe material being dried as the drying operation progresses, and causingsaid action to establish and maintain the predetermined differentconditions of temperature and liumidity within the kiln as the dryingoperation progresses.

8. The improvement in the kiln drying of materials which requiredifferent conditions of temperature and humidity in the course of thedrying operation, which conipi'ises producing Within the kiln acontinuing action indicative of changes in a varying characteristic of arepresentative sample of said material as the drying operationprogresses, and employing said action to establish the desiredconditions of temperature and humidity Within the kiln as the dryingoperation progresses.

9. The improvement in the kiln drying of materials which requiredifferent conditions oi temperature and humidity during the dryingoperation, which comprises predetermining the desired dierent conditionsof temperature and humidity' for the material to be dried, producingwithin the kiln a continuing action indicative of changes in a varyingcharacteristic of a representative sample of the material being dried asthe drying operation progresses, and employing said action to establishthe predetermined different conditions of temperature and humiditywithin the kiln as the drying operation progresses.

l0. The improvement in the kiln drying of materials which requiredifferent conditions of temperature and humidity` during the dryingoperation` which comprises producing Within the kiln a continuing actionindicative of changes in a varying'charactcristic of a representativesample of said material as the drying operation progresses, and causingsaid action to establish and maintain the desired diierent conditions ofrature and humidity within the kiln e drying 'operation pro resses. Theimprovement in t e kiln drying of materials which require differentconditions of temperature and humidity during the drying operation,which comprises redetermining the desired dilierent conditions oftemperature and humidity for the material to be dried, producing withinthe kiln a continuing action lindicative of changes in a va 'ngcharacteristic of a re resentative samp e of the material being ried asthe drying operation progresses, and causing said action to establishand maintain the predetermined dii'erent conditions of temperature andhumidity within the kiln as the drying operation progresses.

y12. The improvement in the kiln drying ofy lumber or wood, whichcomprises producing within the kiln a continuing action indicative "ofchanges in the moisture content of a representative sample of saidlumber or wood as the dryin operation progresses, and transmitting saiaction to a point outside the-kiln.

13. The improvement in the method of drying materials which requiredifferent conditions of temperature and humidity in the course of thedrying operation, w ich comprises automatically controlling thetemperature and humidity of the drying medium to which the material tobe dried is subjected in res onse to changes in a varying characteristicof the material undergoing drying as the drying operation progresscs.

14. The improvement in the method of drying materials which requiredifferent conditions of temperature and humidity in the course of thedrying operation, which comprises automatically controlling Y thetemperature' and humidity of the drying medium to which the material tobe dried is subjected in responsetochanges in a va ing characteristic oa representative samp e of the material undergoing drying as the dryingoperation progresses.

15. The improvement in the method of drying materials which requiredifferent conditions of tem erature and humidity in the course of therying operation, which comprises automatically controllingv the temrature and humidit of the drying me lum to which the material to bedried is subjected in response to the loss in weight of a representativesample of the material undergoing dryin as the drying operationprogresses.

16. e improvement in the kiln drying of materials which requiredifferent conditions of temperature and humidity in the course of therying operation, which comprises producing a continuin action indicativeof the loss in weight o a representative sample of the material beingdried as the tem as t d ing operation ro esses, and causing sgd actionto estab ishgdnd maintain the desired varying conditions of temperature.and humidity within the kiln as the drying operation iogresses. Y

17. T e improvement in the kiln drying of materials which requiredifferent conditions of temperature and humidity in the course of thedrying operation, which comprises predetermining the desired differentconditions of temperature andhumidity for the material to be dried,producing a continuing action indicative of the loss in Weight of arepresentative sample of the material being dried as the dryingoperation progresses, and causing said action to establish and maintainthe predetermined diierent conditions of temperature and humidity withinthe kiln as the drying operation progresses. l

18. The improvement in the kiln drying of lumber or wood, whichcomprises producing an action responsive to the progressive loss inmoisture of arepresentative sample of said lumber or wood as the dryingoperation progresses, and employin said action to establishpredetermined di erent conditions of temperature and humidity within thekiln as the drying operation progresses.

19. The improvement in the kiln drying of lumber or wood, whichcomprises producing within the kiln a continuing action responsive tothe progressive loss in moisture of a representative sample of saidlumber or wood as the drying operation progresses, and causing saidaction to establish and maintain predetermined diii'erent conditions oftemperature and humidity within the kiln as the drying operationprogresses.

20. The improvement in the kiln drying of lumber or `wood, whichcomprises automatically controlling the temperature and humidity of thedrying medium to which the lumber or Wood to be dried is subjected inresponse to the loss in weight of a representative sample of the lumberor Wood Within the kiln as the drying operation progresses.

21. The improvement in the kiln drying of materials which requirediierent conditions of temperature and humidit during the dryingoperation, which comprises causing the progressive loss in moisture of arepresentative sample of the material being dried as the dryingoperation progresses to eiect predetermined adjustments of temperatureand humidity controllers and thereby establishing and maintaining Withinthe kiln as the drying operation progresses predetermined dii'erentconditions of temperature and humidity.

22. The improvement in thekiln drying of materials which requirediilerent conditions o temperature and humidity during the dryingoperation, which comprises establishing, in response to the progressiveloss in moisture of a re resentative sample of the material being riedas the drying operation progresses, the setting of temperature andhumidity controllers o erativcly arranged to substantially maintainwithin the kiln conditions of temperature and humidity corresponding tothe settings thereof.

23. The improvement in the kiln drying of materials which require varyinconditions of temperature in the course o the drying operation, whichcomprises producing an aotion indicative ot changes in said material asthe drying operation progresses, and employing said action to establishthe desired varying conditions of temperature Within the kiln as thedrying operation progresses.

24. The improvement in the kiln drying of materials which requirevarying conditions of tempei'ature in the course of the dryingoperation, which comprises producing an action indicative of changes insaid material as the drying o eration progresses, and employing saidaction to establish the desired varying conditions of humidity withinthe kiln as the drying operation progresses.

25. The improvement in the kiln drying of materials which requiredifferent conditions of temperature as the drying operation progresses,which comprises producing an action responsive to the progressive lossin moisture of said material as the drying operation progresses, andemploying said action to rogressively establish predetermined dierentconditions of temperature within the kiln as the drying operationprogresses.

26. The improvement in the kiln drying of materials which requiredi'erent conditions of humidity as the drying operation progresses,which comprises producing an action responsive to the progressive lossin moisture of said material as the dryin operation progresses, andeinplloyirg sai action to progressively establis pre etermined dii'erentconditions of humidity within the kiln as the drying operationprogresses.

27 The improvement in the kiln drying of materials which require varyingconditions of temperature in the course of the drying operation, whichcomprises producing an action indicative of changes in a varyingcharacteristic of a re resentatlve sample of the material being ried as.the drying operation progresses, and employing said action to proessivel establish and maintain predetermined di erent conditions oftemperature within the kiln as the drying operation progresses.

28. The improvement in the kiln drying of materials which requirevarying conditions of humidity in the course of the drying operation,which comprises producing an action indicative of changes in a varyingVcharacteristic of a representative sample of the material being driedas the dryin operation progresses, and employing sai action toprogressively establish and maintain predetermined different conditionsof humidity within the kiln as the drying operation progresses.

29. The improvement in the method of drying materials which requirediierent conditions of temperature in the course of the dryingoperation, which comprises automatically controlling the temperature ofthe drying medium to which the material to be dried is subjected inresponse to changes in a varying characteristic of a representativesample of the material undergoing drying as the drying operationprogresses.

30. The im rovement in the method of drying materials which requiredilierent conditions of humidity in the course of the drying operationwhich com rises automatically controlling the humidity of the dr ingmedium to which the material to be dried is subjected in response tochanges in a variying characteristic of a representative samp e of thematerial undergoing drying as the drying operation progresses.

31. The improvement in the kiln drying of materials which requiredifferent conditions of temperature during the drying operation, whichcomprises causing the progressive loss in moisture of a re resentativesam le of the material being ried as the drying operation progresses toeect predetermined adjustments of a temperature controller and therebyestablishing and maintaining within the kiln as the drying operationprogresses predetermined different conditions of temperature.

32. The improvement in the kiln drying of materials which requiredifferent conditions of humidity during the drying operation, whichcomprises causing the progressive loss in moisture of a re resentativesample of the material being ried as the drying operation progresses toeiect predetermined adjustments of a humidity controller and therebyestablishing and maintaining within the kiln as the dryin operationprogresses predetermined different conditions of humidity.

The improvement in the kiln drying of materials which require diierentconditions of temperature during the drying operation. which comprisespredetermining thc desired different conditions of temperaiure for thematerial to be dried, producing Within the kiln a continuing actionindicative of changes in a varying characteristic ot a representativesample of the material being dried as the drying operation progrosses,and employing said action to establish and maintain the predetermineddifferent conditions of temperature within the kiln as the dryingoperation progresses.

34. The improvement in the kiln drying of materials which re uircdifferent conditions of humidity during the drying operation, whichcomprises predetermimng the desired di'erent conditions of humidity forthe material to be dried, producing within the kiln a continuing actionindicative of changes in a varying characteristic of a representativesample of the material being dried as the drying operation progresses loand employing said action to establish and maintain the predetermineddiierent conditions of humidity within the kiln as the drying operationrogresses In testimony w ereof ture.

I aix my signala JOHN BERCHMANS WELCH.

34. The improvement in the kiln drying dried as the d in o ration roesses 10 o f materials :which re uire diierent condiand employingIs'idgaetin to estblirh and tions of humidity during the dryingopermaintain the predetermined different conation, which comprisespredetermining the ditions of humidity Within the kiln as the desireddrerent conditions of humidity for drying operation rogresses. thematerial to be dried, producing within In testimony w ereof I affix mysignal5 the kiln a continuing action indicative of ture. changes 1n avarying characteristic of a representative sample of the material beingJOHN BERCHMANS WELCH.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,567 ,559, grantedDecember 29. 1925, upon 'the application of John Berohmans Welch, of NewOrleans, Louisiana, or an improvement in Drying Wood, Lumber, and theLike, errors appear in the printed specification requirin correction asfollows: Page 2, line 44, for the Word kilns read kil/n; pa e 5, ine 19,for the Word conductor read conductors; page 10, line 86, claim for themisspelled word ad read and; page 12, line 20, claim 24, for the Wordtemperature read humidity; and that the said Letters Patent should beread with these corrections therein that the same may conform to therecord of the case in the Patent Oilice.

Signed and. sealed this 20th day of July, A. D. 1926.

[SEAL] M. J. MOORE,

Acting ommssz'ofwr of Patents.

